Ministry of Earth Sciences
Mechanism for Prediction of Rainfall
Rainfall prediction is given in different time scales, i.e. seasonal forecast , extended range forecast , short-medium range forecast  and nowcasts . These forecasts are generated using state of the art weather prediction models based on mathematical equations and physics of atmosphere and oceans.
An improved suite of prediction models has already been implemented operationally at India Meteorological Department  for enhanced shortrange weather forecasting through assimilation of all available Indian and global satellite data in real time.
Since December 2016, IMD is using the Global Forecast System  and Unified model run at National Centre for Medium Range Weather Forecast  operationally every day to generate deterministic forecasts at 12 km horizontal resolution in the short to medium range . The GFS assimilates global conventional atmospheric data as well as the data from satellites and weather radars. There also exists a high resolution meso-scale model with 3 km resolution to provide location specific forecast.
In addition, a high resolution  state of the art Global Ensemble Prediction System  namely Global Ensemble Forecasting System  and Unified model Ensemble Prediction System  was commissioned on 01 June 2018 for generating operational probabilistic weather forecasts for 10 days. The GEPS has enhanced the weather information being provided by the current models by quantifying the uncertainties in the weather forecasts.
Under the National Monsoon Mission, MoES has implemented two state-of-the-art dynamical prediction systems for short range to medium, extended range and seasonal forecasts. All these initiatives have helped to improve the skill of monsoon rainfall forecasts over the country. Since 2017, IMD is using the Monsoon Mission dynamical model to prepare operational seasonal forecast of monsoon rainfall over India.
The above mentioned forecast systems will be improved further for better accuracy with the enhancement in observational systems and advancement in numerical modeling and efforts are on for this purpose. The Ministry of Earth Sciences  has invited proposals from research community for development of artificial intelligence  and machine learning  based tools & techniques for prediction of weather. Scientists at MOES are also involved in developing products based on AI and ML methods.
IMD has a shared mandate with Central Water Commission  for flood forecasting. River basin floods are dealt by the CWC. Flood Meteorological Offices  operated by IMD provide meteorological support to the CWC for issuing flood warnings in respect of the 43 rivers of India covering 153 river basins. CWC issues flood forecasts for about 6 hrs. to 30 hrs. in advance for 176 stations using Quantitative Precipitation Forecast  received from FMOs of IMD and in-situ hydro-meteorological data.
In order to meet specific requirements of flood forecasting, which is provided by Central Water Commission , IMD operates Flood Meteorological Offices  at thirteen locations viz., Agra, Ahmedabad, Asansol, Bhubaneshwar, Guwahati, Hyderabad, Jalpaiguri, Lucknow, New Delhi, Patna, Srinagar, Bengaluru and Chennai. Apart from this, IMD also supports Damodar Valley Corporation  by providing Quantitative Precipitation Forecast  for Damodar river basin areas for their flood forecasting activities.
CWC is working in close association with IMD and State Governments for timely flood forecast whenever the river water level rises above warning level. In order to cater to the services of hydro-meteorological events occurring in short duration of time, IMD has implemented a Flash Flood Guidance System  with the technical help from World Meteorological Organization .
The weather forecasting and early warning systems in the country are comparable to most of the developed countries in the world. Efforts are continuously made to enhance the observational network and the level of efficiency of the forecasting systems based on latest technology including Satellite, Radar and numerical models. During the past few years, IMD has been continuously improving weather prediction services in terms of accuracy, lead time and associated impact.
This information was given by Dr. Harsh Vardhan, Union Minister for Science & Technology, Earth Sciences and Health & Family Welfare in a written reply in Lok Sabha today.